1. Field of the Invention
The invention relates to a recording electrode body for use in an image forming apparatus that forms an image by controlling an electric field, and that can be used in a copier, a printer, a plotter, a facsimile or other similar device. The invention also relates to a method of manufacturing a recording electrode body, and an image forming apparatus that uses the recording electrode body.
2. Description of the Related Art
U.S. Pat. No. 3,689,935 discloses an image forming apparatus that applies image signals to an electrode, that defines apertures, to control the passage of toner particles through the apertures so as to form a desired image on a support body.
The image forming apparatus described in U.S. Pat. No. 3,689,935 includes an aperture electrode body made up of an insulating layer, a continuous shield electrode disposed on one side of the insulating layer, and a plurality of separate control electrodes disposed on the other side of the insulating layer. The control electrodes are insulated from one another. The aperture electrode body has at least one row of apertures, each of which extends through the three layers, that is, the shield electrode, the insulating layer and the control electrodes, on a one-to-one correspondence with the separate control electrodes.
The image forming apparatus further includes a device that selectively provides an electric potential to the control electrodes relative to the shield electrode, a device that supplies charged toner particles to the apertures of the aperture electrode body, a back-plate electrode which is disposed on a side of the support body that is opposite from the aperture electrode body, and to which a high voltage is applied, and a device that positions the support body in a particle passage by moving the support body relative to the aperture electrode body.
The present applicant has proposed in, for example, Japanese Patent Application Laid-Open No. HEI 6-155798, an improved image forming apparatus in which the recording characteristics are considerably improved by disposing a carrier, that carries toner thereon, and an aperture electrode body, so that they are in contact with each other.
The recording head used in this image forming apparatus is illustrated in FIG. 1. A recording head 100 includes an insulating sheet 102 formed of, for example, a polyimide film of 25 to 50 microns in thickness, and a substrate 101 disposed thereon. The substrate 101 has leads 103 that are formed of a copper layer of 8 microns in thickness. Driver ICs 105 are provided on the substrate 101. Multiple apertures 106 are formed near a distal end of the leads 103. Since the apertures 106 are aligned in a straight line at a high density, the apertures 106 are illustrated as a straight line in FIG. 1.
Each of the driver ICs 105 applies an output voltage to the leads 103 so as to form a control electric field around the corresponding aperture 106. Each driver IC 105 is an ordinary IC that is formed mainly from silicon, and that has a logic portion and a driver portion.
However, the above-described recording head is limited from the stand point of miniaturizing the apparatus and reducing its production cost. Specifically, in order to provide a higher resolution of the recording head, it is important to take into account how densely the components of the recording head, such as the apertures of the printing portion, the control electrodes, the driver ICs and other components, can be arranged in the lengthwise direction, that is, how narrow each component can be formed in that direction.
With regard to the apertures and the control electrodes, a processing technology for achieving a pitch of 40 .mu.m or less has been developed. With regard to the driver ICs, advancements in the semiconductor technology have made it possible to achieve a pad pitch of about 40 .mu.m, that is, voltage electrode output pin pitch of about 40 .mu.m.
However, there is a significant problem in a mounting technology for connecting the driver ICs to the control electrodes on the substrate. In particular, the mounting of driver ICs at such a reduced pad pitch cannot be achieved according to the conventional technology.
This problem occurs because the wire bonding method that is normally used merely provides pin connection at a pitch of about 70 microns or greater, Furthermore, since only one lead wire can be connected at a time by the wire bonding method, the connecting process requires a lot of labor and high costs, especially for products that have many pin connections, for example, a high-resolution head.
In a recently developed mounting method that is generally referred to as the flip chip mounting method, ICs are joined with a substrate, facing down. Since the method joins all the leads of each IC to the substrate by one process, the flip chip mounting method can reduce costs. However, the connection pitch that can be practically achieved by this method is only about 100 microns. Therefore, this method cannot be applied to high-resolution recording heads.
However, regardless of which conventional method is employed, there is a significant possibility that a connection will fail since a lot of connections must be formed. Therefore, the conventional mounting methods also have a reliability problem.